Phosphopeptide analysis by positive and negative ion matrix‐assisted laser desorption/ionization mass spectrometry
- 9 August 2001
- journal article
- research article
- Published by Wiley in Rapid Communications in Mass Spectrometry
- Vol. 15 (17) , 1593-1599
- https://doi.org/10.1002/rcm.417
Abstract
This article describes a simple procedure for the detection of phosphorylated peptides by comparable positive and negative ion mode matrix-assisted laser desorption/ionization mass spectrometry measurements. Based on studies with phosphorylated peptides (EAIXAAPFAK, X = pS, pT, pY) and their corresponding non-phosphorylated analogs, it was found that phosphopeptides, which are characterized by a low ionization efficiency in the positive ion mode, exhibit drastically increased signal intensities in the negative ion mode compared to their non-phosphorylated analogs. The effect was successfully used to identify phosphorylated sequences of the commonly used phosphoprotein standards, protein kinase A and β-casein, by peptide mass fingerprint analyses of the corresponding Lys C and trypsin digests using both (positive and negative) ion modes. The comparison of positive and negative ion spectra of a given protein digest (relative intensity[M − H]−/relative intensity[M + H]+) can be used to identify any phosphopeptides present which may then be separated and analyzed further. Copyright © 2001 John Wiley & Sons, Ltd.Keywords
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